Vehicle

ABSTRACT

The front fork of a motorcycle is carried by a steering spindle mounted for angular rotation about the axis of the steering spindle in the steering head member of a motorcycle frame. The steering spindle is rotatable in bearing assemblies at opposite ends of the steering head member of the motorcycle frame, and provision is made for adjustment of the steering head angle by the inclusion in at least one of these bearing assemblies of an eccentric member. The eccentric member is arranged for assembly alternatively in either of two diametrically opposed angular orientations to position the axis of steering spindle in a corresponding one of two angular positions in the central longitudinal vertical plane of the motorcycle frame. A series of eccentric members of different eccentricity may be provided so that a wide range of steering head angle adjustment may be provided. It is known to mount the front fork of a motorcycle in an angularly adjustable pivoted harness to achieve adjustment of the steering head angle, but this is prone to maladjustment during use, while adding to the weight and detracting from the aesthetic value of the machine.

TECHNICAL FIELD

[0001] The present invention relates to a technology which allows a bodyframe to be used commonly on two-, three- and four-wheeled automotivevehicles.

BACKGROUND ART

[0002] Among two-, three- and four-wheeled automotive vehicles, thereare some types of vehicles, like a scooter type vehicle, which include asubstantially horizontal, low floor type foot rest located at a centraland upper area of a body frame. For example, a scooter type motorcycleis known as a “motorcycle” which is disclosed in Japanese PatentLaid-Open Publication No. HEI-11-79044. Further, Japanese Utility ModelRegistration No. 2515092 discloses a scooter type motorcycle entitled “AFrame Structure For A Scooter Type Vehicle”.

[0003] As shown in FIGS. 1 and 4 of the aforementioned Japanese PatentLaid-Open Publication No. HEI-11-79044, the two-wheeled automotivevehicle is the scooter type motorcycle wherein a body frame has a mainframe, for supporting a foot rest, whose front portion is formed with anupright head pipe post which includes a head pipe by which a steeringshaft is rotatably supported to steer a front wheel, and wherein a swingtype power unit with rear wheel is mounted to a rear portion of the mainframe by means of a bearing and is swingable in an up and downdirection.

[0004] As shown in FIGS. 1 and 5 of Japanese Utility Model RegistrationNo. 2515092, the scooter type motorcycle has a structure wherein a bodyframe has a main frame, for supporting a floor portion, whose frontportion extends upward and has at its distal end formed with a head pipewhich front forks are rotatably mounted to steer a front wheel, andwherein a swing type power unit with a rear wheel is mounted to a rearportion of the main frame by means of a link mechanism and is swingablein an up and down direction.

[0005] Since the two-, three- and four-wheeled automotive vehicles aredifferent in car models, in general, these vehicles have front-wheel andrear-wheel peripheral components which are different from one another instructure and dimension. For this reason, it is a usual practice toemploy particular body frames specific for respective car models of thetwo-, three- and four-wheeled automotive vehicles.

[0006] However, the presence of the particular body frames each for eachcar model needs (1) to prepare particular manufacturing dies andinspection gauges specified for body frames of respective car modelswith a resultant increase in the production cost of the dies, (2) toshift production lines each time when altering the kind of body frameswith a resultant deterioration in productivity and an increase inproduction-management steps, and (3) to prepare a large number of kindsof body frames with a resultant increase in management steps, storagecosts and transportation costs. Due to these factors, when manufacturingthe body frames of various kinds, the production cost of the body framesincreases and there is yet room for improvement for addressing the aboveissues.

DISCLOSURE OF THE INVENTION

[0007] It is therefore an object of the present invention to reduce theproduction cost of a body frame for use in two-, three- and four-wheeledautomotive vehicles.

[0008] According to an aspect of the present invention, there isprovided a vehicle which comprises: a body frame having a center framesection for supporting a foot rest, a rear frame section rising uprightfrom a rear portion of the center frame section, and a front framesection rising upright from a front portion of the center frame section;a head pipe formed on the front frame section; and a steering shaftrotatably mounted to the head pipe for steering at least one frontwheel, the head pipe having an adjustment mechanism for adjusting aposition and an angle of a center line of the steering shaft relative toa center line of the head pipe, the rear frame section having aplurality of rear mount portions for selectively mounting plural kindsof rear units including a swinging power unit equipped with rear wheelsand a swing arm equipped with rear wheels.

[0009] When using the body frame of one kind commonly on two-, three-and four-wheeled automotive vehicles, adjusting the adjustment mechanismallows the center line of the steering shaft to be adjusted to desiredpositions and angles relative to the center line of the head pipe so asto cope with the models of the two-, three- and four-wheeled automotivevehicles. As a consequence, even in a case where there is a differencein structure and dimension in peripheral component parts of the frontand rear wheels of the two-, three- and four-wheeled automotivevehicles, it is possible to commonly use the body frame.

[0010] Desirably, the rear units comprise a rear unit for a two-wheeledautomotive vehicle having at least one rear wheel, a rear unit for athree-wheeled automotive vehicle having a pair of right and left rearwheels, and a rear unit for a four-wheeled automotive vehicle having apair of right and left rear wheels, and wherein the rear mount portionsare disposed on a rear wall of the rear frame section in such a manneras to allow the two-wheeled-automotive-vehicle rear unit to be mountedthereto vertically swingably by means of a pivot member, to allow thethree-wheeled-automotive-vehicle rear unit to be coupled theretorollingly and vertically swingably by means of a coupling mechanism, andto allow the four-wheeled-automotive-vehicle rear unit to be coupled tothe rear mount portions at least vertically swingably by means of thecoupling mechanism, for thereby permitting thetwo-wheeled-automotive-vehicle rear unit, thethree-wheeled-automotive-vehicle rear unit, and thefour-wheeled-automotive-vehicle rear unit to be selectively mounted tothe rear mount portions.

[0011] That is, {circle over (1)} the two-wheeled-automotive-vehiclerear unit, which has a structure and dimension optimum for thetwo-wheeled automotive vehicle, {circle over (2)} thethree-wheeled-automotive-vehicle rear unit, which has a structure anddimension optimum for the three-wheeled automotive vehicle, and {circleover (3)} the four-wheeled-automotive-vehicle rear unit, which has astructure and dimension optimum for the four-wheeled automotive vehicle,are suitably prepared, and these rear units are selected and detachablymounted to the body frame. While maintaining a commonality of the bodyframe for the two-, three- and four-wheeled automotive vehicles, it ispossible for the body frame to be selectively and readily mounted withthe two-wheeled-automotive-vehicle rear unit, thethree-wheeled-automotive-vehicle rear unit and thefour-wheeled-automotive-vehicle rear unit.

[0012] In a preferred form, both side portions of the body frame includepillar mount portions to which lower portions of a pillar, which servesas a roof support post, are detachably mounted. Accordingly, whilemaintaining a commonality of the body frame for the two-, three- andfour-wheeled automotive vehicles, it is possible for the body frame tobe readily mounted with various components parts such as a roof, etc.,via the pillar.

[0013] In a specific form, the vehicle comprises a four-wheeledautomotive vehicle which has a pair of right and left rear wheels, andthe center frame section and the front frame section have front portionsformed with front mount segments to which a front frame is detachablymounted, while the front frame includes arm mount segments for mountingswing arms, which support the pair of right and left front wheels, to bevertically swingable, damper coupling segments for coupling upper distalends of front dumpers by which the swing arms are suspended, and asteering mount segment for rotatably supporting the steering shaft.

[0014] Thus, in the present invention, the vehicle is arranged such thatthe front frame is detachably mounted to the body frame so as to supportthe steering shaft and, further, the swing arm is mounted to the frontframe to which the front dumpers are also coupled. Accordingly, whilemaintaining the commonality of the body frame for the two-, three- andfour-wheeled automotive vehicles, it is possible for the front portionof the body frame to be readily mounted with a front suspension systemand a steering system of the four-wheeled automotive vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Certain preferred embodiments of the present invention will bedescribed in detail below, by way of example only, with reference to theaccompanying drawings, in which:

[0016]FIG. 1 is a side elevational view illustrating a two-wheeledautomotive vehicle (motorcycle) according to a first embodiment of thepresent invention;

[0017]FIG. 2 is an enlarged side view of a body frame shown in FIG. 1;

[0018]FIG. 3 is a schematic view illustrating the body frame as seenfrom the direction of numeral 3 shown in FIG. 2;

[0019]FIG. 4 is an exploded perspective view of the two-wheeledautomotive vehicle, with a front wheel omitted;

[0020]FIG. 5 is a schematic side view illustrating on an enlarged scalea detail of a front suspension system and a steering system of a frontportion of the two-wheeled automotive vehicle shown in FIG. 4;

[0021]FIG. 6 is a schematic view illustrating an operation of the frontsuspension system and the steering system shown in FIG. 5;

[0022]FIG. 7 is a cross-sectional view of an adjustment mechanism of asteering shaft shown in FIG. 5;

[0023]FIG. 8 is a cross-sectional view illustrating an example whereinthe steering shaft is mounted to a head pipe such that a center of thesteering shaft is located rearward of a center of the head pipe in FIG.7;

[0024]FIG. 9 is a cross-sectional view illustrating an example whereinthe steering shaft is mounted to and is inclined with respect to thehead pipe such that a lower distal end of the steering shaft is directedrearward in FIG. 7;

[0025]FIG. 10 is a cross-sectional view illustrating an example whereinthe lower distal end of the steering shaft is mounted to and is inclinedwith respect to the head pipe in FIG. 9;

[0026]FIG. 11 is an enlarged view showing, partially in section, a rearwheel support unit shown in FIGS. 1 and 4;

[0027]FIG. 12 is a view illustrating steps for mounting a pivot memberof the rear wheel support unit shown in FIG. 11 to the rear frame of thebody frame;

[0028]FIG. 13 is a view illustrating how to mount front rear wheels ofdifferent diameters in the two-wheeled automotive vehicle shown in FIG.1;

[0029]FIG. 14 is a view illustrating a first modification of the rearwheel support unit according to the first embodiment shown in FIG. 11;

[0030]FIG. 15 is a cross-sectional view taken along line 15-15 of FIG.14;

[0031]FIG. 16 is an exploded perspective view of a two-wheeledautomotive vehicle employing a second modification of the rear wheelsupport unit;

[0032]FIG. 17 is an enlarged side view of the second modification of therear wheel support unit shown in FIG. 16;

[0033]FIG. 18 is a side view illustrating a three-wheeled automotivevehicle according to a second embodiment of the present invention;

[0034]FIG. 19 is an enlarged side view of the rear wheel support unitshown in FIG. 18;

[0035]FIG. 20 is an exploded perspective view of the three-wheeledautomotive vehicle shown in FIG. 18, with a front wheel and a roof beingomitted;

[0036]FIG. 21 is a side view illustrating a four-wheeled automotivevehicle according to a third embodiment of the present invention;

[0037]FIG. 22 is an enlarged side view of the front suspension systemand the steering system shown in FIG. 21;

[0038]FIG. 23 is an enlarged side view of the rear wheel support unitshown in FIG. 21;

[0039]FIG. 24 is an exploded perspective view illustrating thefour-wheeled automotive vehicle shown in FIG. 21, with the roof omitted;

[0040]FIG. 25 illustrates an example alteration for the front suspensionsystem and the steering system shown in FIG. 22 wherein a singlesteering shaft is used; and

[0041]FIG. 26 illustrates a modified form of the body frame shown inFIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

[0042] The following description is merely exemplary in nature and is inno way intended to limit the invention, its application or uses.

[0043] Now, a vehicle according to a first preferred embodiment of thepresent invention is described with reference to an example of atwo-wheeled automotive vehicle (automotive two wheeler) shown in FIGS. 1to 15.

[0044] In FIG. 1, the two-wheeled automotive vehicle 10 of the firstpreferred embodiment is shown as a scooter type motorcycle. Themotorcycle 10 includes a front suspension system 30 and a steeringsystem 40 which are mounted to a front portion of a body frame 20. Arear wheel support structure 80 is mounted to a rear portion of the bodyframe 20. A substantially horizontal, low floor type foot rest (floorstep) 101 is mounted to a central and upper portion of the body frame20. A seat 102 is mounted to a rear and upper portion of the body frame20. In the drawings, reference numeral s 41, 103 and 104 designate ahandle lever, a head lamp and a stand, respectively.

[0045] The motorcycle 10 has a structure wherein a vehicle body issurrounded with a front fender 111, a front cover 112, a handle cover113, a leg shield 114 which covers legs of a vehicle driver, a floorskirt 115, a center cover 116, a rear cover 117 and a rear fender 118.

[0046] The body frame 20 shown in FIG. 2 includes a main frame (a centerframe section) 21 made of a casting product of aluminum alloy andconfigured in a substantially horizontally extending frame structure, ahead pipe post (a front frame section) 22 standing upright at a frontportion of the main frame 21, a head pipe 23 formed at an upper distalend of the head pipe post 22, and a rear upright portion (a rear framesection) 24 standing upright from a rear portion of the main frame 21.

[0047] The main frame 21 plays a roll to support the foot rest 101 (seeFIG. 1) and has a front area formed with a dumper pivot section 21 a.The main frame 21 has front mount segments 21 b which extend forward atright and left sides of the frame. Pillar mount segments 21 c, 21 c areformed at a rear portion of the main frame at both right and left sidesthereof. The head pipe post 22 has a front and lower area formed withright and left frontal mount segments 22 a. The rear upright section 24has upper right and left side portions formed with rear frame mountsegments 24 a, and intermediate right and left side portions formed withrear mount segments 24 b. The rear mount segments 24 b are formed withan axial bore.

[0048] The rear upright section 24 is composed of a unitary structureformed in a reversed U-shaped configuration as viewed from a backside asshown in FIG. 3, and includes right and left upright sections 25, 25 anda cross member 26 bridged between the upright segments 25, 25 at upperareas thereof. The right and left upright sections 25, 25 are unitarilyformed at their rear surfaces with pluralities of rear mount portions 27in vertically aligned relationships. All of the rear mount portions 27are equally spaced from one another by a pitch P1. A symbol CL refers toa center (a center of the vehicle body) of a vehicular width.

[0049] As shown in FIG. 4, the rear wheel support unit 80 of themotorcycle 10 has a structure wherein pivot members 81, 81 aredetachably mounted to the rear parts of the body frame 20 to allow aswing type power unit 91 equipped with a rear wheel to be swingablymounted and the rear wheel 92 is rotatably supported at a rear part ofthe power unit 91.

[0050] The power unit 91 includes an engine 93 and a power transmissionunit 94 assembled in a unitary fashion therewith to transmit poweroutput of the engine to the rear wheel 92, and serves as a rear unit ofthe motorcycle including the single rear wheel 92, i.e., a rear driveunit.

[0051] The rear upright section 24 has right and left rear frame mountsegments 24 a, 24 a, to which a rear frame 95, formed in a U-shapedconfiguration as viewed from the above in a plane, is fixedly secured bymeans of bolts. The rear frame 95 serves to suspend a rear portion ofthe power unit 91 by means of rear dumpers 96.

[0052]FIG. 5 is a left side view of a front portion of the motorcycleaccording to the present invention and shows the front suspension system30 and the steering system 40.

[0053] The front suspension system 30 serves as a swing arm typesuspension which includes a swing arm 32, formed in a U-shape as viewedfrom side, which has a base terminal end 32 a mounted to the front mountsegments 21 b of the main frame 21 by means of a pivot shaft 31 and isswingable in upward or downward, and a wheel shaft holder block 34 whichis supported with a front end of the swing arm 32 by means of a king pin33 to be rotatable in a right and left direction, with the wheel shaftholder 34 being provided with a wheel shaft 35 by which a front wheel 36is rotatably mounted. That is, the front suspension system 30 includesthe swing arm 32 which extends from the front end of the main frame 21toward a front area of the vehicle body in an upwardly curved shape soas to bypass the front wheel 36 such that the front wheel 36 issupported with the swing arm 32 in a cantilever fashion.

[0054] The wheel shaft holder block 34 has a support segment (a king pinmount segment) 34 a to allow the king pin 33 to be mounted to a rear andlower portion of the block, a central area in which the wheel shaft 35is mounted, and a knuckle 34 b which extends forward and upward from thewheel shaft 35. The king pin 33 may be unitarily formed with the wheelshaft holder block 34 by means of the support segment 34 a.

[0055] Further, the front suspension system 30 serves to suspend a baseportion of the swing arm 32 to a dumper pivot section 21 a of the mainframe 21 by means of a front dumper 37. More particularly, an uprightmember 32 b extends upward from the base terminal end 32 a of the swingarm 32 and has its upper distal end to which one distal end of the frontdumper 32 is interconnected by a pin 38, with the other distal end ofthe front dumper 32 being interconnected to the dumper pivot section 21a by a pin 39..

[0056] The steering system 40 has a structure with the followingfeatures (1) and (2).

[0057] (1) A steering shaft 42 is rotatably supported by the head pipe23 and has a lower distal end formed with a connecting member 43 whichin turn is connected to the knuckle 34 b via a link mechanism 50.

[0058] (2) The head pipe 23 includes an adjustment mechanism 60 which isenabled to shift a center lineAl of the steering shaft 42 relative to acenter line of the head pipe 23.

[0059] In particular, the steering system 40 is so arranged that one endof the link mechanism 50 is connected to the knuckle 34 b of the wheelshaft holder block 34 and the other end of the like mechanism 50 isconnected to the steering shaft 42 to allow the steering shaft 42 tosteer the front wheel 36.

[0060] The link mechanism 50 is constructed of a crooked link, which isconfigured in a dog leg shape to be freely bendable to accept upward ordownward movements of the front wheel 36, and which includes first andsecond links 52, 54 between which a connecting segment 55 is directedforward.

[0061] More particularly, the link mechanism 50 includes (1) a firstlink 52 having its one end which is connected to the connecting member43 of the steering shaft 42 by means of a first connecting pin 51 and isswingable vertically, (2) a second link 54 having its one end which isconnected to a distal end of the knuckle 34 b by means of a secondconnecting pin 53 and is swingable vertically, and (3) a universal jointcoupling 56 which is connected to the other ends of the first and secondlinks 52, 54, i.e., to the connecting segment 55, between the first andsecond links 52, 54, which is swingable upward or downward. Theuniversal joint coupling 56 is composed of, for example, a ball joint.

[0062] With such a steering system 40, the king pin 33 is located at aposition offset in a rearward direction from the steering shaft 42 and,when looking at the link mechanism 50 from above, the steering shaft 42remains in an intermediate position between the king pin 33 and theuniversal joint coupling 56. More particularly, when looking at the linkmechanism 50 from the center line A1 of the steering shaft 42, i.e., ina direction of line LO, the steering system 40 has the followingrelationship (1) to (3).

[0063] (1) A connecting center B2 between the front end of the swing arm32 and the king pin 33 is located at a position offset rearward from thecenter line A1 of the steering shaft 42.

[0064] (2) A center D1 of the universal joint coupling 56 is located ata position offset forward by an offset quantity S1 from the center lineA1 of the steering shaft 42.

[0065] (3) The center line B1 of the king pin B1 and the center D1 ofthe universal joint coupling 56 is spaced by a distance S2.

[0066] Thus, it is possible for the connecting center B2 or the centerD1 of the universal joint coupling 56 to be offset rearward or forwardrelative to the center line A1 of the steering shaft 42.

[0067] As the front wheel 36 moves upward or downward, the swing arm 32and the wheel shaft holder block 34 swing upward or downward accordingto the displacement value of the front wheel. As a consequence, thesecond link 54, connected to the knuckle 34 b, and the first link 52 arecaused to swing upward or downward.

[0068]FIG. 6 is a view for illustrating the operation of the frontsuspension system and the steering system shown in FIG. 5 and shows atypical operational view when looking at the front suspension system 30and the steering system 40, shown in FIG. 5, from the line LO.

[0069] However, the connecting center B2 is illustrated in a developedstate on a flat surface F1 perpendicular to the center line A1 of thesteering shaft 42 and intersecting the center D1 of the universal jointcoupling 56 shown in FIG. 5. That is, when assuming that the flatsurface perpendicular to the center line B1 of the king pin 33 andintersecting the center D1 of the universal joint coupling 56 isexpressed as F2, the flat surface F2 is illustrated in a developed stateso as to overlap the aforementioned flat surface F1. When developed assuch, the center line A1 of the steering shaft 42 is parallel to thecenter line Bi of the king pin 33.

[0070] In FIG. 6, the center line A1 of the steering shaft 42, theconnecting center B2 between the front end of the swing arm 32 and thekingpin 33, and the center D1 of the universal joint coupling 56, shownin FIG. 5, refer to a “point A1”, a “point B2” and a “point D1”,respectively.

[0071] Now, the front suspension system 30 and the steering system 40are described below in detail in conjunction with FIGS. 5 and 6.

[0072] When a manipulating angle of the steering shaft 42 remains at azero degree, that is, when the steering shaft remains in a neutralposition, the points A1, B2 and D1 are aligned on the center line CL ofthe vehicle body. From such a neutral position, if the first link 52 ismanipulated rightward with the steering shaft 42 by a manipulating angleα with respect to a forward portion of the vehicle, then the point D1 isdisplaced to a point DR. As a result, the wheel shaft holder block 34and the second link 54 are steered by a steering angle of β about thepoint B2. On the contrary, if the first link 52 is manipulated leftward,similarly, the point D1 is displaced to a point DL. As a result, thewheel shaft holder block 34 and the second link 54 are steered leftward.

[0073] Since the point B2 is offset rearward with respect to the pointA1, the steering angle β is smaller than the manipulating angle α (i.e.,α>β). Thus, the steering power of the steering shaft 42 becomes smallerin value than that attained in a case where there is no aforementionedoffset condition. Adjusting the amount of offset enables the rate of thesteering angle β relative to the manipulating angle α to be varied.

[0074] Also, in a case where the point B2 is offset forward with respectto the point A1, the steering angle β becomes larger than themanipulating angle α (i.e., α<β). Thus, the steering power of thesteering shaft 42 becomes larger in value than that attained in a casewhere there is no aforementioned offset condition.

[0075]FIG. 7 is a cross sectional view illustrating peripheries of thesteering shaft and the adjustment mechanism.

[0076] The head pipe 23 has a through-hole 23 a, which extends upwardand downward, for receiving the steering shaft 42. The through-hole 23 ahas a diameter relatively larger than that of the steering shaft 42 soas to allow the center line A1 of the steering shaft 42 to intersect thecenter line C1 of the head pipe 23 at an arbitrary angle. For example,the through-hole 23 a may be formed in an elliptic-shaped hole which iselongated in a fore and aft direction as compared to the diameter of thesteering shaft 42, or in a large sized hole with a true circle. Thesteering shaft 42 and the connecting member 43 are coupled to oneanother by press fitting the steering shaft 42 to the connecting member43 and subsequently welding lower end portions.

[0077] The adjustment mechanism 60 is so constructed that a top plate 61and a bottom plate 71 are mounted to upper and bottom walls of the headpipe 23 to be replaceable and the steering shaft 42 is inserted throughand rotatably supported by a through-bore 61 a of the top plate 61 and athrough-bore 71 a of the bottom plate 71. The top plate 61 serves tosupport the steering shaft 42 by means of a first bearing 62 and a locknut 66. Likewise, the bottom plate 71 serves to support the steeringshaft 42 by means of a second bearing 72.

[0078] In particular, the top plate 61 includes a body unit 61 b formedwith the through-bore 61 a, an engaging portion 61 c which engages thethrough-hole 23 a of the head pipe 23, a flange 61 d held in abuttingengagement with an upper distal end of the head pipe 23, and apositioning recess 61 e which engages a convex portion of the head pipe23 for positioning.

[0079] The first bearing 62 includes an outer race 63 which engages thethrough-bore 61 a of the top plate 61, an inner race 64 which is screwedonto a male thread 42 a of the steering shaft 42, a plurality of balls65 interposed between the outer and inner races 63, 64, and a retainer,which is not shown, for retaining the balls 65. The inner race 64 playsa roll of an adjustment nut.

[0080] The bottom plate 71 includes a body unit 71 b formed with thethrough-bore 71 a, an engaging portion 71 c which engages thethrough-hole 23 a of the head pipe 23, a flange 71 d held in abuttingengagement with a lower distal end of the head pipe 23, and apositioning recess 71 e which engages a convex portion of the head pipe23 for positioning.

[0081] The second bearing 72 includes an outer race 73 which engages thethrough-bore 71 a of the bottom plate 71, an inner race 74 which isfitted to the steering shaft 42, a plurality of balls 75 interposedbetween the outer and inner races 73, 74, and a retainer, which is notshown, for retaining the balls 55.

[0082] As will be apparent from the foregoing description, it ispossible for the steering shaft 42 to be rotatably mounted in the headpipe 23 by means of the top and bottom plates 61, 71 and the first andsecond bearings 62, 72. Reference numeral 44 designates a fixture boltfor fixing a handle bar 41 to an upper end of the steering shaft 42.

[0083]FIG. 7 shows that the center line A1 of the steering shaft 42 issubstantially parallel to and is located forward of the center line C1of the head pipe 23. As a matter of course, the centers of thethrough-bores 61 a, 71 a of the top and bottom plates 61, 71, which aremounted to the top and bottom walls of the head pipe 23, are alignedwith the center line A1 of the steering shaft 42.

[0084]FIG. 8 shows an example wherein the steering shaft 42 is mountedto the head pipe 23 such that the center line A1 of the steering shaft42 is located in parallel to and rearward of the center line C1 of thehead pipe 23.

[0085] The centers of the through-bores 61 a, 71 a of the top and bottomplates 61, 71, which are mounted to the top and bottom walls of the headpipe 23, coincide with the center line A1 of the steering shaft 42.Replacement of the top and bottom plates 61, 71 shown in FIG. 7 with thetop and bottom plates 61, 71 shown in FIG. 8 allows the center line A1of the steering shaft 42 to be shifted. FIG. 9 shows an example whereinthe steering shaft 42 is mounted to the head pipe 23 such that thecenter line A1 of the steering shaft 42 is arranged to intersect at aforward area with the center line c1 of the head pipe 23 by locating alower end of the steering shaft 42 at a more forward place than thecenter line C1 of the head pipe 23.

[0086] The centers of the through-bores 61 a, 71 a of the top and bottomplates 61, 71, which are mounted to the top and bottom walls of the headpipe 23, coincide with the center line A1 of the steering shaft 42.Replacement of the top and bottom plates 61, 71 shown in FIG. 7 with thetop and bottom plates 61, 71 shown in FIG. 9 allows the center line A1of the steering shaft 42 to be shifted.

[0087]FIG. 10 shows an example wherein the steering shaft 42 is mountedto the head pipe 23 such that the center line A1 of the steering shaft42 is arranged to intersect at a rearward area with the center line C1of the head pipe 23 by locating a lower end of the steering shaft 42 ata more rearward place than the center line C1 of the head pipe 23.

[0088] The centers of the through-bores 61 a, 71 a of the top and bottomplates 61, 71, which are mounted to the top and bottom walls of the headpipe 23, coincide with the center line A1 of the steering shaft 42.Replacement of the top and bottom plates 61, 71 shown in FIG. 7 with thetop and bottom plates 61, 71 shown in FIG. 10 allows the center line A1of the steering shaft 42 to be shifted.

[0089] As will be apparent from the foregoing description, by replacingthe plural top plates 61 and the plural bottom plates with the otherones according to the diameter of the front wheel 36 (see FIG. 5), it ispossible for the center line A1 to be altered to an arbitrary positionor at an arbitrary angle with respect to the center line C1 of the headpipe 23. changing the position or the angle of the center line A1 altersthe offset quantities S1, S2 shown in FIGS. 5 and 6, thereby enablingthe rate of the steering angle β relative to the manipulation angle α tobe settled to an optimum level.

[0090]FIG. 11 is an enlarged view for illustrating a detail of the rearwheel support unit 80.

[0091] The rear wheel support unit 80 features a structure wherein thebody frame 2o is formed with a plurality (i.e., four pieces in anillustrated embodiment of FIG. 11) of the rear mount portions 27 toallow the mounting height of the pivot member 81 to be arbitrarilyadjusted. Further, the rear wheel support unit 80 features that, byturning upside down the pivot member 81, the height position of thepivot point PV is enabled to be altered.

[0092] The pivot member 81 is composed of a unitary product whichincludes first and second coupling segments 82, 83 and a pivot segment84 integral with the first and second coupling segments 82, 83. Thepivot segment 84 is located rearward of the first and second couplingsegments 82, 83.

[0093] The first and second coupling segments 82, 83 are spaced from oneanother by a pitch P2 which corresponds to the pitch between upper andlower bolt apertures ad is equal to a value two times (P2=2×P1) thepitch P1 between the rear mount portions 27, 27. The point P3,which-remains at an intermediate height between the first and secondcoupling segments 82, 83, lies in a position at a value ½ the pitch P2.

[0094] Mounting the first and second coupling segments 82, 83 to thearbitrary ones of the rear mount portions 27, 27 by means of bolts 85,85 enables the pivot member 81 to be coupled to the rear wall of thebody frame 20.

[0095] The pivot segment 84 allows hanger segments 97 of the power unit91 to be mounted in an upward and downward swinging relationship withthe pivot shaft 87 via a rubber bush 86. Here, the center (i.e., thecenter of the pivot segment 84) of the pivot shaft 87 refers to a pivotpoint PV. The pivot member 81 lies in a position closer to the firstcoupling segment 82 by a dimension P4, i.e., lies in the pivot point PVremaining at the offset position.

[0096] FIGS. 12(a) to (d) are views for illustrating the operation ofaltering the height position of the pivot point PVB shown in FIG. 11. Inthese drawings, further, the four pieces of rear mount portions 27involve, in a sequence from the above, a first rear mount segment 27A, asecond rear mount segment 27B, a third rear mount segment s 27C, andfour rear mount segments 27D.

[0097]FIG. 12(a) shows a situation wherein the pivot member 81 isbrought into abutting engagement with the body frame 20 from a rearwardarea and the first coupling segment 82 is mounted to the first rearmount portion 27A while the second coupling segment 83 is coupled to thethird rear mount portion 27C. The pivot point PV remains at a height H1.

[0098]FIG. 12(b) shows a situation wherein the pivot member 81 is turnedupside down from the position shown in FIG. 12(a) and the height of thepivot point PV is altered. In this instance, the second coupling segment83 is mounted to the first rear mount portion 27A, and the firstcoupling segment 82 is mounted to the third rear mount portion 27C. Thepivot point PV lies at a height H2 which is lower than the height H1 bya height h1.

[0099]FIG. 12(c) shows a situation wherein the pivot member 81 isaligned in the same direction as FIG. 12(a) and the first couplingsegment 82 is mounted to the second rear mount portion 27B while thesecond coupling segment 83 is mounted to the fourth rear mount portion27D. The pivot point PV lies at a height H3 which is higher than theheight H2 by a height h2.

[0100] FIG, 12(d) shows a situation wherein the pivot member 81 isturned upside down from the position shown in FIG. 12(c) and the heightof the pivot point PV is altered. In this instance, the second couplingsegment 83 is mounted to the first rearmount portion 27B, and the firstcoupling segment 82 is mounted to the fourth rear mount portion 27D. Thepivot point PV lies at a height H4 which is lower than the height H3 bya height h3.

[0101] As is apparent from the foregoing description, the presence ofthe plurality of rear mount portions 27 aligned vertically on the bodyframe 20 allows the first and second coupling segments 82, 83 to beselectively and detachably mounted onto the rear mount portions 27,thereby enabling the mounting height of the pivot member 81 to bearbitrarily adjusted. As a result, the mounting height of the power unit91 (see FIG. 11) may be arbitrarily adjusted to a desired value.

[0102] Further, the presence of the pivot member 81 adapted to be turnedupside down to be mounted to the rear mount portions 27, . . . , allowsthe height position of the pivot point PV to be altered. As a result,the height position of the power unit 91 (see 11) may be arbitrarilyaltered to a desired value.

[0103]FIG. 13 is a schematic view of the motorcycle of the firstpreferred embodiment of the present invention with a view to comparingthe following situations (1) and (2).

[0104] (1) The motorcycle 10 includes the front wheel 36 of a large sizeand the rear wheel 92, which are shown by a solid line. The frontsuspension system 30, the steering system 40 and the rear wheel supportunit 80 assume respective positions as shown by solid lines. In theseinstances, the wheel base between the front wheel 36 and the rear wheel92 has a value of WB1, a caster angle of θ1 (i.e., a caster angle of thefront wheel 36) at the center line B1 of the king pin, a trail T1 of thefront wheel 36 and the pivot point PV remaining at the height H2.

[0105] (2) The motorcycle 10 includes the front wheel 36 of a small sizeand the rear wheel 92, which are shown by a phantom line. The frontsuspension system 30, the steering system 40 and the rear wheel supportunit 80 assume respective positions as shown by phantom lines. In theseinstances, the wheel base between the front wheel 36 and the rear wheel92 has a value of WB2, a caster angle of θ2 at the center line B1 of theking pin, a trail T2 of the front wheel 36 and the pivot point Pvremaining at the height H4.

[0106] When the front wheel 36 of the large diameter is replaced withthe front wheel 36 of the small diameter, the caster angles θ1, θ2 andthe trails T1, T2 may be settled to optimum values with a view toproviding an improved driving characteristic, and, in accordance withthe caster angles θ1, θ2 and the trails T1, T2, the front suspensionsystem 30 and the steering system 40 may be suitably settled to have anoptimum operational relationship.

[0107] For example, in order to settle a manipulating position OP of ahandle lever 41 to the same height as that of the front wheel beforereplacement thereof even in a case where the front wheels 36 ofdifferent diameters are replaced, the inclination and the position ofthe steering shaft 42 may be suitably altered to desired values withrespect to the head pipe 23. In addition, when the rear wheel 92 of alarge diameter and the rear wheel 92 of a small diameter are replaced,the mounting height of the pivot member 81 may be adjusted.

[0108] In summary of the motor cycle 10, in accordance with the diameterof the front wheel 36, the center line A1 of the steering shaft 42 maybe altered to have an arbitrary position and an inclined angle.Consequently, even in a case where the size of the front wheel 36 isaltered, there is no need for changing the position of the head pipe 23which is integrally formed with the body frame 20. Further, inaccordance with the size of the rear wheel 92, the mounting height ofthe pivot member 81 maybe arbitrarily altered with respect to the bodyframe 20.

[0109] Due to these results, it is possible for the body frame 20 to becommonly used even when the diameter of the front wheel 36 and thediameter of the rear wheel 92 are altered, with a resultant decrease inmanufacturing cost of the motorcycle 10.

[0110] Further, by suitably setting the caster angles θ1, θ2 and thetrails T1, T2, it is possible to commonly use the steering shaft 42 ofthe steering system 40 and the link mechanism 50. Also, the frontsuspension system 30 needs only modification of the swing arm 32.

[0111] Furthermore, by suitably adjusting the inclination and the angleof the center line A1 of the steering shaft 42 with respect to the headpipe 23 while changing the lengths of the first and second links 52, 54,in accordance with the diameter of the front wheel 36, it is possible tovary the rate of the steering angle of the front wheel 36 relative tothe manipulating angle of the steering shaft 42. With the variation insuch a rate, the manipulating force of the steering shaft 42 may bevaried to an optimum level.

[0112]FIG. 14 shows a first modified form of the rear wheel support unitof the motorcycle of the first preferred embodiment.

[0113] The rear wheel support unit 120 of the first modified formfeatures that the front portion of the power unit 91 is mounted to thepivot member 81 by means of a vibration-proof link mechanism 121 and isswingable upward or downward. Other structural components are the sameas the rear wheel support unit 80 of the first preferred embodimentshown in FIGS. 11 and 12 and, therefore, bear the same referencenumerals, with a detailed description of the same being omitted.

[0114] The vibration-proof link mechanism 121 serves as a mechanismwherein a pivot shaft 122 of the power unit 91 is located rearward ofthe pivot shaft 87 of the pivot member 81 and the pivot shafts 87, 122are connected to one another by means of a vibration-proof link 123 suchthat the power unit 91 is swingably mounted to the pivot shaft 87 bymeans of the vibration-proof link 123.

[0115] In such a structure, upper and lower distal ends of thevibration-proof link 123 are mounted with rubber mount segments 124,124, to which stopper rubbers 125, 125 made of resilient material arefixedly secured.

[0116] The upper and lower stopper rubbers 125, 125 are located so as tolye in abutting contact with the first and second coupling segments 82,83 of the pivot member 81. Accordingly, the swinging movement of thevibration-proof link 123 is resiliently restricted with the rearsurfaces of the first and second coupling segments 82, 83 and the upperand lower stopper rubbers 125, 125. That is, the first and secondstopper rubbers 125, 125 provide shock absorbing functions during upwardand downward swinging movements and restoring functions to be effectedtoward a neutral position shown in the drawings.

[0117]FIG. 15 shows a structure wherein the pivot shaft 87 is insertedthrough the pivot segment 84 by means of a rubber bush 86 and, further,the pivot shaft 122 is inserted through the hanger segment 97 of thepower unit 91 by means of a rubber bush 126 such that the pivot shafts87, 122 are interconnected with the vibration-proof link 123. Referencenumeral 127 designates an auxiliary link.

[0118]FIGS. 16 and 17 show a second modified form of the rear wheelsupport unit of the first preferred embodiment.

[0119] In FIG. 16, the rear wheel support unit 130 of the secondmodified form features that the front portion of the power unit 91 ismounted to the right and left rear mount segments 24 b, 24 b of the rearupright section 24 by means of a vibration-proof link mechanism 131 andis swingable upward or downward. In particular, the vibration-poof linkmechanism 131 serves as a mechanism wherein right and leftvibration-proof links 133, 133 are swingably mounted to the right andleft rear mount segments 24 b, 24 b by means of first pivot shafts 132,132, respectively, and the hanger segments 97, 97 of the power unit 91are swingably mounted to the vibration-proof links 133, 133 by means ofsecond pivot shafts 134, 134, respectively. Both the right and leftvibration-proof links 133, 133 are interconnected to one another by acoupling bar 135.

[0120]FIG. 17 shows a structure wherein the front portion of the powerunit 91 is mounted to the sides of the rear upright section 24 by meansof the vibration-proof mechanism 131.

[0121] Among the right and left vibration-proof links 133, 133 shown inFIG. 16, upper and lower end of the left vibration-proof link 133 carryrubber mount segments 136, 136 to which stopper rubbers 137, 137 made ofresilient material are mounted. The upper and lower stopper rubbers 137,137 are placed in abutting contact with a rear surface of an uprightportion 25. Accordingly, the swinging movement of the vibration-prooflink 133 is resiliently restricted with the rear surface of the uprightportion 25 and the associated stopper rubbers 137, 137. That is, theupper and lower stopper rubbers 137, 137 provide shock absorbingfunctions during upward and downward swinging movement of thevibration-proof link 133 and restoring functions to be effected towardthe neutral position shown in the drawings. Reference numerals 138, 138designate rubber bushes, respectively.

[0122] As will be apparent from the foregoing description, themotorcycle 10 of the second modified form allows the body frame 20 ofthe motorcycle 10 shown in FIGS. 1 to 13 to be commonly used.

[0123] Now, a vehicle of a second preferred embodiment is describedbelow with reference to an example of a three-wheeled automotive vehicle(automotive three wheeler) shown in FIGS. 18 to 20.

[0124] The three-wheeled automotive vehicle 140 shown in FIG. 18 is ascooter type tricycle motor vehicle which includes a single front wheel36 and two rear wheels 175, 175. The three-wheeled atutomotive vehicle140 has a structure wherein a front suspension system 30 and a steeringsystem 40 are mounted to a front portion of a body frame 20, a rearwheel support 160 is mounted to a rear portion of the body frame 20, asubstantially horizontal, low floor type foot rest (floor step) 141 ismounted to an intermediate and upper portion of the body frame 20 and aseat assembly 142 is mounted to the rear and upper portion of the bodyframe 20.

[0125] The front suspension system 30 and the steering system 40 havethe same structures as those of the motorcycle 10 of the first preferredembodiment shown in FIGS. 1 to 13, with the same component parts bearingthe same reference numerals and a detailed description of the same beingomitted.

[0126] The three-wheeled automotive vehicle 140 has a structure whereina screen garnish 144 is mounted to a front portion of the head pipe 23by means of a stay 143, a wind screen 145 stands upright from the screengarnish 144, a front distal end of a roof 146 is mounted to an upperdistal end of the wind screen 145, a roof support pole, i.e., a pillar147 stands upright from a rear portion of the body frame 20 and a reardistal end of the roof 146 is mounted to a support segment 147 a of thepillar 147. In the drawings, reference numerals 151, 152, 153, 154, 155and 156 designate a head lamp, a wiper, a front cover, a handle cover, aleg shield which covers the driver's legs, and a receiver box,respectively.

[0127] In FIG. 19, a rear wheel support unit 160 features that the bodyframe 20 has the rear surface formed with four rear mount portions 27 towhich a swinging type power unit 171 with a rear wheel is mounted bymeans of a coupling mechanism 161 in a rolling and swingablerelationship. Here, the word “rolling” refers to the movement that thepower unit 171 rotates about a center of a coupling shaft 163, whichextends in a fore and aft direction of the coupling mechanism 161,relative to the body frame 20.

[0128] The coupling mechanism 161 includes a front mounting flange 162,the coupling shaft 163 mounted to the mounting flange 162 and extendingin the fore and aft direction of the vehicle, a coupling case 165rotatably coupled to the coupling shaft 163 by means of a dampermechanism 164, and a hanger 166 fixed to the coupling case 165. Thecoupling mechanism 161 is detachably mounted to the body frame 20 byfixing the mounting flange 162 to the rear mount portions 27 by means ofa plurality of bolts 167.

[0129] The dumper mechanism 164 has a shock absorbing function duringrotating movement of the coupling case 165 relative to the couplingshaft 163 and a restoring function to restore the neutral position,i.e., a so-called dumper function.

[0130] The hanger 166, which extends rearward and upward from thecoupling case 165, has an intermediate position in a lengthwisedirection to which a hanger segment 172 of the power unit 171 isswingably mounted by means of a bracket 168 and a pivot shaft 169, and arear end position to which a rear end of the power unit 171 is suspendedby means of a rear dumper 173. The power unit 171 unitarily incorporatesan engine 174 and a power transmission unit 176 for transmitting poweroutput of the engine 174 to rear wheels 175, 175 and serves as athree-wheeled-automotive-vehicle rear unit, equipped with the right andleft rear wheels 175, 175, i.e., a rear unit.

[0131] In FIG. 20, the body frame 20 of the three-wheeled automotivevehicle 140 concerns the following features.

[0132] (1) The main frame 21 plays a roll to support the foot rest 141shown in FIG. 18.

[0133] (2) Placing an auxiliary plate 181 onto the main frame 21 andfixing the same by bolts increases the rigidity of the body frame 20.

[0134] (3) Fixing lower ends of the pillar 147 to right and left pillarmount portions 21 c, 21 c of the main frame 21 allows the lower ends ofthe pillar 147 to be detachably mounted to both sides of the body frame20 in an easy manner. Accordingly, it is possible for various componentparts, such as the roof 146 (see FIG. 18), etc., to be mounted to thebody frame 20 via the pillar 147.

[0135] (4) A rear frame 182 can be fixed to right and left rear framemount portions 24 a, 24 a of the rear upright section 24 by bolts.

[0136] Upon consideration of an optimum driving characteristic of thethree-wheeled automotive vehicle 140, adjusting the adjustment mechanism60 which has been discussed as the first preferred embodiment withreference to FIGS. 5 to 10 enables the center line A1 of the steeringshaft 42 to be settled to an arbitrary position and angle. Consequently,even when modifying the motorcycle 10 of the first preferred embodimentshown in FIG. 1 to the three-wheeled automotive vehicle 140, there is noneed for changing the position of the head pipe 23 of the body frame 20.In addition, the power unit 171 can be coupled the plural rear mountportions 27 formed on the rear surfaces of the body frame 20 by means ofthe coupling mechanism 161, thereby enabling the body frame 20 of themotorcycle 10 shown in FIGS. 1 to 13 to be commonly used for thethree-wheeled automotive vehicle 140.

[0137] Now, a vehicle of a third preferred embodiment is described belowin detail with reference to a four-wheeled automotive vehicle(automotive four wheeler) shown in FIGS. 21 to 25.

[0138] In FIG. 21, the four-wheeled automotive vehicle 200 is a scootertype four-wheeled motor vehicle wherein a substantially horizontal,lower floor type foot rest (a floor step) 201 is mounted to a centraland upper portion of the body frame 20, a seat 202 is mounted to a rearand upper portion of the body frame 20, a front suspension system 230and the steering system 240 are mounted to a front portion of the bodyframe 20, a rear wheel support unit 260 is mounted to the rear portionof the body frame 20, and which includes right and left two front wheels236 and right and left two rear wheels 268.

[0139] The four-wheeled automotive vehicle 200 has a structure wherein ascreen garnish 204 is mounted to a front portion of the head pipe 23 bymeans of a stay 203, a wind screen 205 stands upright from the screengarnish 204, a front distal end of a roof 206 is mounted to an upperdistal end of the wind screen 205, a roof support pole, i.e., a pillar207 stands upright from a rear portion of the body frame 20 and a reardistal end of the roof 206 is mounted to a support segment 207 a of thepillar 207. In the drawings, reference numerals 211, 212, 213, 214, 215,216, 217 and 218 designate a bumper, a head lamp, a wiper, a frontcover, a handle cover, a leg shield which covers the driver's legs, areceiver box and a rear cover, respectively.

[0140]FIG. 22 shows a front suspension system 230 and a steering system240 which are located at a front area of the four-wheeled automotivevehicle 200.

[0141] The four-wheeled automotive vehicle 200 is constructed such thata rear portion of a front frame 223 is detachably mounted to front mountsegments 21 b of the main frame (the center frame portion) 21 and frontmount segments 22 a of the head pipe post (the front frame section) 22by means of bolts 221, 222.

[0142] The front frame 223 includes arm mount segments 224 for swingablymounting a swing arm 232, a dumper coupling segment 225 for couplingupper ends of front dumpers 233 by which a swing arm 232 is suspended, asteering support segment 226 for rotatably supporting a second steeringshaft 242, and a pillar mount segment 227 for mounting the pillar 207(see FIG. 21).

[0143] The front suspension system 230 includes the front frame 223, theswing arm 232 swingably mounted to the arm mount segments 224 of thefront frame 223 by means of a pivot shaft 231, and the front dumper 233having an upper end coupled to the dumper coupling segments 225 of thefront frame 223 by dumper coupling bolts and a lower end coupled to theswing arm by dumper coupling bolts for suspending the swing arm 232. Theswing arm 232 supports right and left two front wheels 236 as shown inFIG. 24.

[0144] The steering system 240 has the following features (1) and (2).

[0145] (1) A first steering shaft 42′ is rotatably supported by the headpipe 23, and the second steering shaft 242, which is different from thefirst steering shaft 42′, is connected to the connecting member 43formed at the lower distal end of the first steering shaft 42′ by meansof a link mechanism 241.

[0146] (2) The head pipe 23 has a structure which includes theadjustment mechanism 60 which changes the center line A1 of the steeringshaft 42′ relative to the center line of the head pipe 23.

[0147] Since the first steering shaft 42′, the coupling member 43 andthe adjustment mechanism 60 have the same structures as the steeringshaft 42, the connecting member 43 and the adjustment mechanism 60 whichhave been discussed with reference to the first preferred embodimentshown in FIGS. 5 and 7 to 10, a detailed description of these componentparts is herein omitted.

[0148] The link mechanism 241 is composed of a crooked link mechanismwhich is foldable in an up and down direction and which includes a firstlink 244, a second link 246 and a coupling member 247 for coupling theselinks. One distal end of the first link 244 is coupled to the connectingmember 43 of the first steering shaft 42′ by means of a first connectingpin 243 to be swingable in an up and down direction. One distal end ofthe second link 246 is coupled to an upper end of the second steeringshaft 242 by means of a second connecting pin 245 to be swingable in anup and down direction. Other distal ends of the first and second links244, 246 are coupled to the connecting member 247 by means of auniversal joint coupling 248. The connecting member 247 is enabled to beswingable vertically by means of the universal joint coupling 248. Theuniversal joint coupling 248 is made of, for example, a ball joint.

[0149] In the steering system 240, the second steering shaft 242 islocated such that the center of the second steering shaft 242 is offsetrearward from the center of the first steering shaft 42′. That is, whenviewing from the center line LO, the first steering shaft 41′ remains inan intermediate position between the second steering shaft 242 and theuniversal joint coupling 248.

[0150] The steering support segment 226 has a through-bore 226 aextending in an up and down direction to receive the second steeringshaft 242. The through-bore 226 a has a diameter of a relatively largesize to allow the second steering shaft 242 to be displaced in a radialdirection.

[0151] The front frame 223 has a top plate 251 and a bottom plate 253which are detachably mounted to upper and bottom walls of the steeringsupport segment 226, respectively. The top plate 251 has a first bearing252. The bottom plate 253 has a second bearing 254. The second steeringshaft 242 is supported with these first and second bearings 252, 254. Alower distal end of the second steering shaft 242 is connected to a tierod 257 via a rod connecting segment 256.

[0152] The rear wheel support unit 260 of the four-wheeled automotivevehicle is shown in FIG. 23. The rear-wheel support unit 260 has astructure wherein a swing type power unit 265 with rear wheels iscoupled to the plural rear mount portions 27, formed at the rear wallsof the body frame 20, via the coupling mechanism 161 to have a rollingeffect and to be swingable in an upward or downward direction. Here, theword “rolling” refers to the movement that the power unit 265 rotatesabout the shaft, extending in a fore and aft direction of the couplingmechanism 161, relative to the body frame 20. The coupling mechanism 161of the present preferred embodiment has the same structure as thecoupling mechanism 161 forming part of the rear wheel support unit 160of the motor-tricycle 140 of the second preferred embodiment and,therefore, bears the same reference numerals to omit a detaileddescription of the same.

[0153] The rear wheel support unit 260 has a structure wherein a baseportion of a hanger 263 is mounted to the coupling case 165 of thecoupling mechanism 161 and the hanger 263 is arranged to extend rearwardto have rear distal ends to which hanger segments 266 of the power unit265 is mounted by means of pivot shafts 264 and is swingable in anupward or downward direction. The rear wheel support unit 260 may beconstructed so as to couple at least the power unit 265 to theaforementioned rear mount portions 27 by means of the coupling mechanism161 in a vertically swingable relation.

[0154] A rear frame 271 is mounted to a rear end of the body frame 20and extends rearward. The power unit 265 is suspended from the rearframe 271 by means of a rear dumper 272. The power unit comprises a rearunit which includes an engine 267, and a power transmission mechanism269 for transmitting power output of the engine 267 to the rear wheels268, which are incorporated in a unitary fashion.

[0155]FIG. 24 is an exploded view of the four-wheeled automotive vehicleaccording to the present invention.

[0156] The body frame 20 of the four-wheeled automotive vehicle 200 hasthe following features.

[0157] (1) The main frame 21 plays a roll to support the foot rest 201(see FIG. 21).

[0158] (2) Fixing lower ends of the pillar 207 to right and left pillarmount portions 21 c, 21 c of the main frame 21 allows the lower ends ofthe pillar 207 to be detachably mounted to both sides of the body frame20 in an easy manner. Accordingly, it is possible for various componentparts, such as the roof 206 (see FIG. 21), etc., to be mounted to thebody frame 20 via the pillar 207.

[0159] (3) Extending right and left pillar extensions 207 b, 207 bforward from lower distal ends of the pillar 207 allows front distalends of the pillar extensions 207 b, 207 b to be detachably mounted tothe pillar mount segment 227 of the front frame 223. The pillarextensions 207 b, 207 b enable the body frame 20 to be reinforced.

[0160] (4) The rear frame 271 is enabled to be fixed to the rear framemount segments 24 a, 24 a of the rear upright section 24.

[0161] The front suspension system 230 is constructed such that wheelshaft holder blocks 237, 237 are mounted to distal ends of the right andleft swing arms 232, 232 by means of king pins 232 a, 232 a to bepivotable in a clockwise or counterclockwise direction and the frontwheels 236, 236 are rotatably mounted to the wheel shaft holder blocks237, 237 by means of wheel shafts 238, 238.

[0162] The steering system 240 is constructed such that right and lefttie rods 257, 257 are connected to one another by means of a rodconnecting member 256 of the second steering shaft 242 and knuckles 239,239 of the wheel shaft holder blocks 237, 237 are coupled to distal endsof the tie rods 257, 257.

[0163] From the foregoing description, the four-wheeled automotivevehicle 200 is summarized as follows.

[0164] Upon consideration of an optimum driving characteristic of thefour-wheeled automotive vehicle 200, adjusting the adjustment mechanism60 enables the center line A1 of the steering shaft 42 to be settled toan arbitrary position and angle. Consequently, even when modifying themotorcycle 10 of the first preferred embodiment shown in FIG. 1 to thefour-wheeled automotive vehicle 200, there is no need for changing theposition of the head pipe 23 of the body frame 20. In addition, thepower unit 265 can be coupled the plural rear mount portions 27 formedon the rear surfaces of the body frame 20 by means of the couplingmechanism 261. Accordingly, it is possible for the body frame 20 of themotorcycle 10 shown in FIGS. 1 to 13 to be commonly used for thefour-wheeled automotive vehicle 200.

[0165] Further, the four-wheeled automotive vehicle 200 is constructedsuch that the front frame 223 is detachably mounted to the main frame 21and the head pipe post 22 to support the steering shaft 242 while, inaddition thereto, the swing arms 232, 232, which support the right andleft two front wheels 236, 236, are mounted to the front frame 223 andthe swing arms 232, 232 are suspended by means of the front dumpers 233,233. Accordingly, while maintaining a commonality of the body frame 20,it is possible for the front suspension system 230 and the steeringsystem 240 of the four-wheeled automotive vehicle 200 to be readilymounted to the front portion of the body frame 20.

[0166]FIG. 25 is a view for illustrating modifications of the frontsuspension system and the steering system of the four-wheeled automotivevehicle according to a third preferred embodiment.

[0167] The front suspension system 230 and the steering system 240 ofthe modified forms feature that the link mechanism 241 and the steeringshaft 242 shown in FIG. 22 are dispensed with and, by extending thefirst steering shaft 42 downward, the first steering shaft 42 serves forthe second steering shaft 242, too. Other structures are the same as thefour-wheeled automotive vehicle 200 shown in FIGS. 21 to 24 and,therefore, bear the same reference numerals for omitting a redundantdescription.

[0168] In particular, a long steering shaft 42 is rotatably mounted tothe head pipe 23 and the steering mount segment 226 and the lower distalend of the steering shaft 42 is connected to the tie rod 257 via the rodconnecting member 256.

[0169] In such a four-wheeled automotive vehicle 200, the head pipe 23and the front frame 223 include the adjustment mechanism 60. Theadjustment mechanism 60 has a structure wherein the steering shaft 42 issupported only with the first bearing 62 of the top plate 61 fixed tothe top wall of the head pipe 23, and the second bearing 254 of thebottom plate 253 fixed to the bottom wall of the steering mount segment226.

[0170] As shown in FIGS. 7 to 10, replacement of the plurality of topplates 61 and the plurality of bottom plates 253, which have thethrough-bores formed in different positions for receiving the steeringshaft 42, allows the center line A1 of the steering shaft 42 to bedisplaced in an arbitrary position or at an arbitrary angle relative tothe center line of the head pipe 23.

[0171] From the foregoing description, the four-wheeled automotivevehicle 200 of the modified form is summarized below.

[0172] Upon consideration of an optimum driving characteristic of thefour-wheeled automotive vehicle 200, adjusting the adjustment mechanism60 enables the center line A1 of the steering shaft 42 to be settled toan arbitrary position and angle. Consequently, even when modifying themotorcycle 10 of the first preferred embodiment shown in FIG. 1 to thefour-wheeled automotive vehicle 200, there is no need for changing theposition of the head pipe 23 of the body frame 20. In addition, thepower unit 265 can be coupled the plural rear mount portions 27 formedon the rear surfaces of the body frame 20 by means of the mountingflange 261. Accordingly, it is possible for the body frame 20 of themotorcycle 10 shown in FIGS. 1 to 13 to be commonly used for thefour-wheeled automotive vehicle 200 of the modified form.

[0173] Further, the four-wheeled automotive vehicle 200 of the modifiedform is constructed such that, like the four-wheeled automotive vehicle200 shown in FIGS. 21 to 24, the steering shaft 42 is supported with thefront frame 223 and further, the swing arm 232 is mounted to the frontframe 223 to which the upper distal end of the front dumper 233 iscoupled. Accordingly, while maintaining a commonality of the body frame20, it is possible for the front suspension system 230 and the steeringsystem 240 of the four-wheeled automotive vehicle 200 to be readilymounted to the front portion of the body frame 20.

[0174]FIG. 26 is a view for illustrating a modified form of the bodyframe and corresponds to FIG. 3.

[0175] The body frame 20 of the modified form features the provision of(1) three pieces of vertically arranged rear mount portions 27, and (2)flat rest seats 281, 282 formed on the left upright segment 25. Otherstructures are the same with the body frame 20 shown in FIGS. 2 and 3and bear the same reference numerals to omit a detail description.

[0176] In summary of the foregoing description, when commonly using thebody frame 20 of one kind in the motorcycle 10, the three-wheel vehicle140 and the four-wheel vehicle 200, it is possible for the center lineA1 of the steering shaft 42 to be settled to an arbitrary position andangle by adjusting the adjustment mechanism 60. Also, it is possible forthe body frame 20 to be selectively mounted with the rear units ofplural kinds, such as the rear units 91, 171, 200 of the motorcycle, thethree-wheel vehicle and the four-wheel vehicle, respectively.Consequently, among the motorcycle 10, the three-wheel vehicle 140 andthe four-wheel vehicle 200, even when there is a difference in structureand dimension (various parameters) in the front wheels 36, 236 and therear wheels 175, 268, it is possible for the body frame 20 to becommonly used, resulting in a decrease in a production cost of the bodyframe 20.

[0177] Furthermore, an optimum two-wheeled-automotive-vehicle rear unit91, an optimum three-wheeled-automotive-vehicle rear unit 171 and anoptimum four-wheeled-automotive-vehicle rear unit 265 can be suitablyselected for the motorcycle 10, the three-wheel vehicle 140 and thefour-wheel vehicle 200, respectively, and thetwo-wheeled-automotive-vehicle rear unit 91, thethree-wheeled-automotive-vehicle rear unit 171 and thefour-wheeled-automotive-vehicle rear unit 265 can be selectively mountedto the plural rear mount portions 27 of the body frame 20. Accordingly,while maintaining the commonality of the body frame 20 in thetwo-wheeled automotive vehicle 10, the three-wheeled automotive vehicle140 and the four-wheeled automotive vehicle 200, it is possible for thebody frame 20 to be selectively and readily mounted with thetwo-wheeled-automotive-vehicle rear unit 91, thethree-wheeled-automotive-vehicle rear unit 171 and thefour-wheeled-automotive-vehicle rear unit 265.

[0178] In the illustrated embodiments discussed above, further, theuniversal joint couplings 56, 248 may comprise isochronous jointcouplings which provides interconnections between the first links 52,244 and the second links 54, 246, or may be composed of ball joints, theuniversal joints or equivalents thereof.

[0179] Further, the outer race 63 of the first bearing 62 maybeunitarily formed with the top plate 61, and the outer race 73 of thesecond bearing may be formed with the bottom plate 71 in a unitaryfashion.

[0180] Further still, the two-wheeled-automotive-vehicle rear unit 91,the three-wheeled-automotive-vehicle rear unit 171 and thefour-wheeled-automotive-vehicle rear unit 265, which serve as the rearunits, are not intended to be limited to the swinging type power unitequipped with the rear wheels, but may be composed of a swing armequipped with the rear wheels.

[0181] In addition, the pillars 147, 207 are not limited to the roofsupport post and may be utilized for various uses such as, for example,posts for mounting a rain shelter member which conceals peripheries ofthe seats of the three-wheeled automotive vehicle 140 and thefour-wheeled automotive vehicle 200.

Industrial Applicability

[0182] By using the body frame common to vehicles of different models,the manufacturing cost of the body frame can be decreased, with aresultant useful value in the production of two-, three- andfour-wheeled automotive vehicles.

1. A vehicle comprising: a body frame having a center frame section forsupporting a foot rest, a rear frame section rising upright from a rearportion of said center frame section, and a front frame section risingupright from a front portion of said center frame section; a head pipeformed on said front frame section; and a steering shaft rotatablymounted to said head pipe for steering at least one front wheel, saidhead pipe having an adjustment mechanism for adjusting a position and anangle of a center line of said steering shaft relative to a center lineof said head pipe, said rear frame section having a plurality of rearmount portions for selectively mounting plural kinds of rear unitsincluding a swinging power unit equipped with rear wheels and a swingarm equipped with rear wheels.
 2. The vehicle of claim 1, wherein saidrear units comprise a rear unit for a two-wheeled automotive vehiclehaving at least one rear wheel, a rear unit for a three-wheeledautomotive vehicle having a pair of right and left rear wheels, and arear unit for a four-wheeled automotive vehicle having a pair of rightand left rear wheels, and wherein said rear mount portions are disposedon a rear wall of said rear frame section in such a manner as to allowsaid two-wheeled-automotive-vehicle rear unit to be mounted theretovertically swingably by means of a pivot member, to allow saidthree-wheeled-automotive-vehicle rear unit to be coupled theretorollingly and vertically swingably by means of a coupling mechanism, andto allow said four-wheeled-automotive-vehicle rear unit to be coupled tosaid rear mount portions at least vertically swingably by means of thecoupling mechanism, for thereby permitting saidtwo-wheeled-automotive-vehicle rear unit, saidthree-wheeled-automotive-vehicle rear unit, and saidfour-wheeled-automotive-vehicle rear unit to be selectively mounted tosaid rear mount portions.
 3. The vehicle of claim 1 or 2, wherein bothside portions of said body frame include pillar mount portions to whichlower portions of a pillar, which serve as a roof supporting post, aredetachably mounted.
 4. The vehicle of claim 2, wherein said vehiclecomprises a four-wheeled automotive vehicle having a pair of right andleft rear wheels, wherein said center frame section and said front framesection have front portions formed with front mount segments to which afront frame is detachably mounted, and wherein said front frame includesarm mount segments for mounting swing arms, which support said pair ofright and left front wheels, to be swingable vertically, damper couplingsegments for coupling upper distal ends of front dumpers by which saidswing arms are suspended, and a steering mount segment for rotatablysupporting said steering shaft.